[erlang-questions] low level packet access from erlang

Garry Hodgson garry@REDACTED
Mon Jul 8 04:18:58 CEST 2013

On 07/07/2013 09:37 AM, Michael Santos wrote:

 > There were a few bugs: TCP options were left out of the
 > record to binary conversion and the length of the payload
 > was left out of the checksum.

after i posted i made my own version that included the opts
and the wireshark errors went away, so i figured it was that.
didn't know about the payload length issue, though, so mine
might still have that problem. i wonder if that could be causing
it to still not work despite (hopefully) well formed packets.

 > Also, use pkt:makesum/1 to calculate the checksum.
 > This should work: TestSum = pkt:makesum( [ IPv4, Tcp, TcpPayload ] ),

yes, i was using that at first, then switched to call my own
versions. i'll retrofit once i turn latest version into rpm form.

 > You may still see some checksum mismatches if your
 > system uses TCP checksum offloading.

oh, goodie. more things to trip over.

thanks a lot for your help.

Garry Hodgson
AT&T Chief Security Office (CSO)

"This e-mail and any files transmitted with it are AT&T property, are confidential, and are intended solely for the use of the individual or entity to whom this e-mail is addressed. If you are not one of the named recipient(s) or otherwise have reason to believe that you have received this message in error, please notify the sender and delete this message immediately from your computer. Any other use, retention, dissemination, forwarding, printing, or copying of this e-mail is strictly prohibited."

More information about the erlang-questions mailing list